<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>移除选项</title>
</head>
<body>
  <form>
    <select name="location" id="selLocation">
      <option value="Sunnyvale, CA">Sunnyvale</option>
      <option value="Los Angeles, CA">Los Angeles</option>
      <option value="Mountain View, CA">Mountain View</option>
      <option value="">China</option>
      <option>Australia</option>
    </select>
  </form>
  <script>
    const selectbox = document.forms[0].elements.location;

    selectbox.remove(0);

    selectbox.options[0] = null;  // 还可以
  </script>
</body>
</html>